Conversion of hydrocarbons



Feb 20,1945.

FRACTIONATORS FRACTIONATOR A. R. GOLDSBY 2,370,030

CbNVERSION OF HYDROCARBONS Filed Aug. 31, 1940 SEPARATOR RECYCLED N-BUTANE RECYCLED ISOBUTANE C PARAFFIN FEED HEATER ARTHUR R. GOLDSBY BY A INVENTfi? v M H S A TORNEYS Patented Feb. 20, 1945 OFFICE CONVERSION OF HYDROCARBONS Arthur R. Goldsby, Beacon, N. Y., assig'nor, by mesne assignments,-to The Texas Company, New York, N.Y., a corporation of Delaware Application August 31, 1940, Serial No. 354,950

7 Claims.

particularly with the production of high anti knock branch chain hydrocarbons suitable for the manufacture of motor fuel from branch chain and straight chain parafiins of lower molecular weight.

The invention contemplates broadly a combination rocess involving alkylation of isoparafiin hydrocarbons with olefins to produce branch chain saturated hydrocarbons, and dehydrogenating normal paraffin hydrocarbons to produce olefin hydrocarbons for charging to the alkylation reaction.

More specifically, the invention contemplates subjecting a hydrocarbon charge comprising olefins, normal parafilns and isoparafiins to an alkylation reaction to form branch chain saturated hydrocarbons, separating unconverted normal and lsoparafiiin hydrocarbons from the treated hydrocarbons, recycling the separated isoparamn hydrocarbons to the alkylation reaction, dehydrogenating the separated normal paraflin hydrocarbons to produce straight chain olefins and passing the resulting olefins to the alkylation reaction.

This application is a continuation-in-part of pending application, Serial No. 169,136, filed October 15, 1937, for Conversion of hydrocarbons.

In accordance with the invention, an olefinic charge comprising essentially straight chain olefins, such as propylene, normal butylenes and normal pentylenes is subjected to reaction in the presence of an alkylation catalyst, such as concentrated sulfuric acid with a paraflin hydrocarbon liraction, such as a C4 traction containing normal and isobutane. Alkylating conditions are maintained during the reaction, whereby isobutane is alkylated with the olefins to produce branch chain saturated hydrocarbons within the motor fuel boiling range. The products of reaction are withdrawn and subjected to fractionation, separating therefrom fractions'respectively rich in normal butane and isobutane. The isobutane is recycled, at least in part, to the alkylation reaction, while the normal butane fraction is subjected to catalytic dehydrogenation to produce normal butylenes and the resulting butylenes are then passed to the alkylation reaction. a

An object ofthe invention is to provide an olefin feed for the alkylation reaction which consists essentially of straight chain oleflns and is relatively free rrom isobutylene. It has been point range.

found that where the feed to the dehydrogenation reaction comprises normal or straight chain parafiins, the dehydrogenated product consists essentially of straight chain olefins. In other words, substantially no molecular rearrangement occurs so that normal butane upon dehydrogenation yields normal butylenes only.

A further object is to utilize the alkylation operation as a means of'purifying the charge to the dehydrogenation step. The alkylation treatment where the alkylation catalyst comprises concentrated sulfuric acid is effective in removing sulfur compounds, such as hydrogen sulfide, methyl mercaptan and also in removing low boiling amines, which compounds cause poisoning of dehydrogenation catalysts.

The hydrocarbons treated and the products obtained may vary within wide limits. By treating normally gaseous hydrocarbons, it is possible to obtain products within the motor fuel boiling Also by treating a mixture of lower boiling normally liquid hydrocarbons and normally gaseous hydrocarbons, it is possible to obtain alkylated products within the gasoline boiling point range. By treating higher boiling liquid hydrocarbons and normally gaseous hydrocarbons, it is possible to obtain higher boiling products including those of the upper boiling.

point range of gasoline or kerosene, gas oil and on up to hydrocarbons within the boiling point range of lubricating oils or. higher. The higher boiling point products may also be obtained as a result of secondary reactions whereby the primary alkylation products are further alkylated to obtain higher boiling materials or homologs, resulting from seconda y or tertiary alkylation reactions.

In the alkylation of paraflins with olefins, the alkylation of an isoparamn takes place relatively easily in the presence or a suitable alklyation catalyst, and under proper. conditions. Thus the alkylation of an isoparaflln with an olefin takes place smoothly and rapidly in the presence of 93-95% sulifuric acid at ordinary temperatures. For example, isobutane may be readily alkylated with normally gaseous olefins, under the conditions specified, to form higher molecular weight isoparaifins. Instead of isobutane, higher iso paraflins, such as isopentane, isohexane, may be used. Likewise, instead of the normally gaseous olefins, higher boiling point oleflns may be used.

The dehydrogenation of arafllns may be obtained efllciently by contacting the parafiins with a dehydrogenation catalyst under elevated temperatures. A satisfactory catalyst-for this pun pose is chromic oxide, preferably chromic oxide gel or chromic oxide mounted on activated alumina. When paraflin hydrocarbons, such as normally gaseous paraffin hydrocarbons, are contactedwith chromic oxide gel at temperatures of around 500-1200 F. and preferably around GOO-1100" F., rapid splitting of hydrogen from the paraffins to form olefins take place. Likewise, dehydrogenation of normally liquid paraffln hydrocarbons may be obtained.

In practicing the process of the present invention, it is advantageous to adjust conditions and regulate the reactions to obtain maximum conversion into the desired products. The determination of these conditions will be dependent more or less upon the skill of the operator. However, certain conditions may be specified although they are not to be construed as a limitation on the process. In general it is desirable to maintain a, predetermined conversion per pass of paraflins into olefins, whereby it is possible to determine the proportion of isoparafiin to be added to the reaction products. In general it is desirable to add the isoparaifins ina quantity equal to the conversion per pass of the paraflins into olefins in the dehydrogenation step and preferably to maintain the concentration of the isoparaffins considerably in excess of the concentration of olefins. For example, the isoparafiins may be 25-50 or even 100% or more in excess of thequantity of the olefins. The amount can be determined by the nature of the final prodnets and adjusted to obtain the maximum yield of the particular boiling point product desired. Likewise, secondary reactions can be materially eliminated by the amount of catalyst and the extent and character of the contact.

The invention will be more fully understood from the following description of the invention I read in connection with the accompanying drawing which shows diagrammatically one form of apparatus for carrying out the process of the invention.

Referring to the drawing, the paraflin hydrocarbon feed consisting essentially of a normal paramn, such as normal butane, from a subsequent stage of the process, to which reference will be made later, is drawn through the line I bythe pump 2, and forced through a heating coil 3 located in a furnace 5. In the heating coil 3, the hydrocarbons are heated to sufiicient temperatures whereby on contact with the dehydrogenation catalyst the splitting of hydrogen takes place smoothly. Temperatures of about 600- 1050 F. are satisfactory and ordinarily atmospheric or relatively low superatmospheric pressures are used. The hot products are transferred through the line I to a dehydrogenator 8 containing a. dehydrogenation catalyst. It is preferred to use chromic oxide gel in granular form which-may be suitably disposed within the tower 8 in such Ta manner as to obtain intimate contact between the catalyst and the hydrocarbons. A conversion of around 15 to 50% per pass may be maintained The reaction products are transferred through line Ill to fractionator II. This fractionator is maintained under a moderate pressure and low temperatures obtained either by cooling in the tower or in the transfer line Ill. It is desirable to obtain substantially complete condensation of the dehydrogenated hydrocarbons whereby permanent gases, comprising mainly hydrogen, may be eliminated from the top of the fractionator through valve controlled line II. The condensate containing normal oleflns resulting from the dehydrogenation is withdrawn from the bottom of the fractionator l2 through the line I5 and forced by the pump 16 through the line l8 to the alkylation chamber 20.

A C4 hydrocarbon fraction comprising mainly normal butane and isobutane is supplied from a. source not shown by a pump 22 through a line 23 which communicates with the line 18 previously mentioned. This paraffinic fraction introduced through the line 23 advantageously comprises sufficient isoparafiln so as to enable the maintaining of the proper ratio of isoparaffin to olefin in the alkylation reaction, whereby alkylating conditions are realized.

The alkylation chamber 20 is supplied with the sulfuric acid alkylation catalyst through the line 25. The alkylation reaction may be carried out under ordinary atmospheric temperatures, for example from about 0-100 F. and preferably around temperatures of about 30-60 F. It is preferable to maintain the hydrocarbons in the liquid phase, maintaining sufficient pressure to prevent substantial vaporization. Means are provided in the tower 20 for obtaining intimate contact and by maintaining a catalyst disposed in the tower in a comminuted form if of solid character or by'suitable means for agitation in case the catalyst is a liquid. When using sulfuric acid, the hydrocarbons may flow concurrently through the tower with rapid agitation. The products are withdrawn from the tower through line 27 to the separator 28 wherein the catalyst carried through may be separated from the 011. This separator is useful in case a liquid catalyst is used whereby the catalyst is allowed to settle and is withdrawn from the bottom of the separator through the line 30 and may be recycled if desired through a line 3|. The hydrocarbons are withdrawn from the top of the separator through the line 32 and passed to the lower portion of fractionator 35.

The alkylated hydrocarbons are subjected to fractionation in the fractionator 35 so as to produce a distillate fraction comprising normally gaseous and normally liquid hydrocarbons and a residual fraction comprising those hydrocarbons boiling above the motor fuel range. This residual fraction is drawn oil? from the bottom of the fractionator' through a valve controlled pipe 36.

The distillate fraction is removed through a pipe 31 leading to a fractionator 38.

In the fractionator 38 normally gaseous constituents including normal butane and isobutane are separated as a distillate fraction leaving a residual fraction comprising alkylated hydrocarbons within the motor fuel boiling range. This motor fuel fraction is drawn off from the bottom of the fractionator 38 through a valve controlled pipe 39.

The distillate fraction comprising normally gaseous hydrocarbons is conducted through a pipe 40 to a fractionator ll. Gaseous constituents which are undesirable for recycling through the system may be released from the top of the fractionator ll through a valve controlled pipe 42.

A fraction comprising isobutane is drawn of! from the fractionator ll as a side stream through a pipe 43 by which means it is returned, all or in part, to the pipe 23, communicating with pipe I. which leads to the alkylator 2|. In this way the isobutane is recycled, all or in part to the alkylation reaction.

A hydrocarbon fraction consisting essentially of normal butane is drawn off from the bottom of the fractionator 4| through a valve controlled pipe 44 and, all or in part, conducted through a pipe 46 communicating with the previouslymentioned pipe l and through which the normal butane is charged to the heater 3 of the dehydrogenation operation.

Many details have been omitted from the drawing for purposes of simplification. It is intended that various pipes, valves, etc. may be used as required by one skilled in the art. Also, any number of dehydrogenation, alkylation and fractionation towers may be employed. It is contemplated that the fractionation towers may be operated to produce motor fuel products of any desired boiling range. Provision may be made for recycling the higher boiling portion of the alkylate to the .alkylation reaction.

While not shown in the drawing, it is nevertheless contemplated that the alkylated hydrocarbons leaving the separator 28 will be subjected to treatment with caustic solution or other alkali to neutralize and remove entrained acid and also to remove other impurities including sulfur compounds.

It is also contemplated that the normal olefin feed to the alkylation reaction may be augmented by the addition of normal olefins from an extraneous source and which may be introduced to the alkylation stage through a valve controlled pipe 5b.

Thus, in operating the process, the oleflnic charge passing through pipe I5 to alkylator 20 comprises normal butylenes. Charging conditions are maintained so that the olefinic feed is combined with isobutane in substantial molar excess of the olefins and the mixture subjected to intimate contact at temperatures in the range 30-60 F. with concentrated sulfuric acid. The makeup acid added to the reaction zone should be acid containing about 96-100% H2504. The acid within the reaction zoneshould be maintained at a concentration in excess of about 88-90% H2804.

The hydrocarbon reaction products are fractionated to obtain an alkylation product boiling within the gasoline boiling range andcontaining a large .amount of isooctanes. The unreacted normally gaseous hydrocarbons consist largely of butane and some isobutane. These hydrocarbons are subjected to fractionation so as to produce fractions respectively rich in normal butane and isobutane.

The normal butane fraction is then passed to the heater 5, ,wherein it is heated to about 750 F. and then passed to the dehydrogenator 8, wherein it is subjected to contact with chromic oxide gel. The time of contact is regulated, whereby approximately 25% conversion per pass is obtained. The products of conversion are then passed to the fractionator l2 to remove gases incluing hydrogen, and thereafter passed to the alkylation zone.

scope thereof, and therefore only such limitations should be imposed as are indicated, in the appended claims.

I claim:

1. Aprocess for the conversion of low boiling hydrocarbons into normally liquid hydrocarbons of higher antiknock value which comprises passing low boiling hydrocarbons, including olefins, paraifins and isoparaifins, to an alkylation zone, subjecting the oleiins to contact in said zone with iso'parairin hydrocarbons in the presence of an alkylation catalyst under conditions of alkylation, such that isoparafiins are alkylated by the olefins to produce branch chain saturated hydrocarbons within the motor fuel boiling range, withdrawing the reacted hydrocarbon mixture from the reaction zone, separating u'nreacted normal parahins irom the alkylated hydrocarbons, subjecting the separated normal pararlins to dehydrogenation under conditions such that the sphttlng of hydrogen takes place and oleilns are produced and passing the sc-produced olenns to the alkylation reaction.

2. A process ior the conversion of normally gaseous hydrocarbons into normally liquid hydrocaroons of high antilmock value, which comprises sub ecting a mixture of normally gaseous hydrocarbons comprising normal butane, isobutane and olefihs to the action of an alkylation catalyst under alkylating conditions whereby the isobutane is aikylated by'the olefins to form normally liquid hydrocarbons, separating the normally liquid hydrocarbons from the reaction products, also separating from the reaction products a normally gaseous hydrocarbon fraction consisting mainly of normal butane, subjecting said fraction to dehydrogenation whereby the normal butane is converted essentially to normal butylenes and passing said last mentioned butylenes to the alkylation operation.

3. A process for the manufacture of high antiknock gasoline hydrocarbons, which comprises subjecting a normally gaseous hydrocarbon fraction, composed essentially of C4 hydrocarbons including normal butane, isobutane and butylenes, to alkylation in the presence of concentrated sulfuric acid whereby the isobutane is alkyla d with the butylenes to form high antiknock gasoline hydrocarbons, separating said gasoline hy-.

drocarbons from the reaction products, also separating from the reaction products the normal butane, catalytically dehydrogenating said normal butane to form normal butylenes and charging said butylenes-to the alkylation operation.

. 4. A process for the conversion of low boiling hydrocarbons into normally liquid hydrocarbons of higher antiknock value, which comprises subjecting an oleflnic fraction comprising essentially normal olefins selected from the group consisting of normal butylenes and normal pentylenes and mixtures thereof to alkylation in the presence of strong sulfuric acid with an isoparafllnic fraction selected from the group consisting of C4 and C5 parafllns and mixtures thereof and containing a substantial proportion of normal paraflin in addition toisoparailin, whereby the normal olefins are aikylated by the isoparaffin to produce branch chain saturated hydrocarbons within the motor fuel boiling range, separating the resulting alkylate from unreacted lower boiling hydrocarbons, separating from the unreacted lower boiling hydrocarbons a normal paraflin fraction, catalvtically dehydrogenating the normal paraflln fraction to convert a portion thereof to the corresponding normal oleflns,

passing the resulting oleflns to the alkylation zone to furnish the olefinic charge to said zone.

5. A continuous cyclic process for the conversion of a normally gaseous straight chain Daraflln and an isoparaflln into normally liquid hydrocarbons of high antiknock value suitable for motor fuel, which comprises continuously feeding the normally gaseous straight chain paraffin and isoparaflin into an alkylation reaction zone together with normally gaseous olefins produced in a subsequent step of the process, agitating the said hydrocarbons in liquid phase in the presence of an alkylation catalyst in said zone maintained under alkylating conditions, whereby the olefins are alkylated by the isoparaflln to produce branch chain saturated hydrocarbons within the motor fuel boiling range, continuously removing reaction products from said zone and separating the'products into a hydrocarbon phase and a catalyst phase, iractionating the hydrocarbon phase to separate normally liquid motor full hydrocarbons and also a normal parailin fraction, subjecting at least a part of the normal parafiln fraction to dehydrogenation under conditions such that hydrogen is split oif and olefins are produced, and passing the so-produced olefins to the alkylation reaction zone to supply the above mentioned olefinic charge thereto.

6. A continuous cyclic process for the conver sion of normal butane and isobutane into normally liquid hydrocarbons of high anti-knock value suitable for motor fuel, which comprises continuously feeding a mixture of normal butane and isobutane into an alkylation reaction zone together with an olefinic charge consisting largely of butylenes produced in a subsequent step of the process, agitating the said hydrocarbons in liquid phase in the presence of an alkylation catalyst in said zone maintained under alkylating conditions and wherein the isobutane is maintained in substantial molar excess of the butylenes, whereby the butylenes are alkylated by the isobutane to produce branch chain saturated hydrocarbons within the motor fuel boiling range, continuously removing reaction products from said zone and separating the products into a hydrocarbon phase and a catalyst phase, fractionating the hydrocarbon phase to separate the motor fuel hydrocarbons and also a normal butane fraction, subjecting at least a part of the normal butane fraction to catalytic dehydrogenation under conditions such that hydrogen is split oil and butylenes are produced and passing the said butylenes to the alkylation reaction zone to supply the above mentioned butylene charge thereto.

7. In the manufacture of substantially saturated hydrocarbons within the gasoline boiling range and of high anti-knock value from a lowboiling isoparaijin and a low-boiling normal paraflin, the cyclic method which comprises continuously introducing the said low-boiling isoparaffin and low-boiling normal paraflin together with olefins produced in a subsequent step of the process into contact with an alkylation catalyst ina reaction Zone under alkylating conditions, with the low-boiling isoparaffin in substantial molar excess oi the olefin, whereby isoparafiin is alkylated with the olefin to produce an alkylate of substantially saturated hydrocarbons Within the gasoline boiling range and of high anti-knock value, separating hydrocarbon reaction products from the catalyst and fractionating the hydrocarbon reaction products into a normally liquid alkylate and a fraction. rich in the said low-boiling normal paraffin, subjecting at least a part of the said-low-boiling normal paraihn fraction to a dehydrogenation operation to produce olefins therefrom, and passing at least a part of said olefins to the said alkylation operation to supply said aforementioned olefin charge thereto.

ARTHUR R. GOLDSBY. 

